In general, electronic devices may use a keypad to enter information into the device. Examples of electronic devices using a keypad include cell phones, telephones, personal data assistants, computers, mini-computers, faxes and hand-held medical devices such as glucose meters and drug infusion pumps. In general, the keypad for such electronic devices includes a circuit board, a frame or substrate and a set of key switches mounted in holes on the frame. When a key switch is clicked, the space between the key switch and the circuit board is closed and a contact at the circuit board is triggered that causes the circuit board to output a corresponding electrical signal.
Gaps may exist between the components of the key switches and the frame, or substrate, allowing ingress of external environmental contaminants such as water or hand lotion into the inside of the keypad assembly which can adversely affect the performance of the keypad. Over-molding processes are generally used to seal the gaps that may exist between the components of the key switches and the frame. However, during the over-molding process, the over-molded material may exert enough pressure on the components of the key switches that the space between the key switches and the circuit board is flattened such that the keypad will not function. Also, materials such as silicone-containing materials used in keypads, bonded onto a substrate do sometimes not fully adhere to a plastic frame, which may allow external contaminants to enter the keypad assembly.
Therefore, applicants recognize a need for a manufacturing method in which the space between the key switch (switch cavity) and the circuit board is maintained during the over-molding process. Applicants also recognize a need for an over-molded layer material that will form a tight seal over the keypad components and the frame or substrate.